A regular octagon has eight axes of symmetry. There are four corresponding vertex lines, four parallel edge midpoint lines and one ***8 line. A figure surrounded by eight equal-length line segments, each with an internal angle of 135, is called a regular octagon. Every corner of a regular octagon is equal in size and every side is equal in length.

If the area s of a regular octagon is known, its side length a = √ (s √ (2+2 √ 2)) and perimeter a = 8× (s √ (2+2 √ 2)).

If the longest diagonal is known, the side length can be converted by the area formula.

If the side length a is known, the perimeter a = 8× a

If the radius of the circumscribed circle is known, it is converted according to the area formula.